Electrical current sensing circuit, printed circuit board assembly and electrical current sensor device with the same

Abstract

An electrical current sensing circuit of the present invention comprises a Wheatstone bridge circuit having at least four magnetoresistive elements connecting and a pair of output terminals, the magnetoresistive elements adapted for sensing an external magnetic field with a first direction generated by a carrying-current electrical conductor, and outputting a differential signal; and a negative feedback circuit connecting with the output terminals, actuated by the differential signal and generated a magnetic field with a second direction that is opposite to the first direction, thereby decreasing the impact of the temperature drift to the magnetoresistive element character. The present invention can eliminate the temperature drift under a changing environment and, in turn obtain an accurate output voltage.

1 . An electrical current sensing circuit comprising:
 a Wheatstone bridge circuit having at least four magnetoresistive elements connecting and a pair of output terminals, the magnetoresistive elements adapted for sensing an external magnetic field with a first direction generated by a carrying-current electrical conductor, and outputting a differential signal; and   a negative feedback circuit connecting with the output terminals, actuated by the differential signal and generated a magnetic field with a second direction that is opposite to the first direction, thereby eliminating the impact of the temperature drift to the magnetoresistive element character.   
     
     
         2 . The electrical current sensing circuit according to  claim 1 , wherein the four magnetoresistive elements are divided into a first element pair and a second element pair that have two opposed pinning directions, which are perpendicular to the first direction of the external magnetic field. 
     
     
         3 . The electrical current sensing circuit according to  claim 2 , wherein the negative feedback circuit comprises a preamplifier and a main wire, the preamplifier is connected with the output terminals, and the main wire is configured between the first element pair and second element pair and the configuring direction of the main wire is vertical with the pinning directions of the first element pair and the second element pair. 
     
     
         4 . The electrical current sensing circuit according to  claim 2 , wherein the distance between the first element pair and the carrying-current electrical conductor is different from that between the second element pair and the carrying-current electrical conductor. 
     
     
         5 . The electrical current sensing circuit according to  claim 2 , wherein the distance between the first element pair and the carrying-current electrical conductor is the same with that between the second element pair and the carrying-current electrical conductor. 
     
     
         6 . The electrical current sensing circuit according to  claim 2 , wherein the first element pair has a first sensitivity and a first saturation point, and the second element pair has a second sensitivity and a second saturation point. 
     
     
         7 . The electrical current sensing circuit according to  claim 6 , wherein the first sensitivity is equal to the second sensitivity, and the first saturation point is not equal to the second saturation point. 
     
     
         8 . The electrical current sensing circuit according to  claim 6 , wherein the first sensitivity is not equal to the second sensitivity, and the first saturation point is not equal to the second saturation point. 
     
     
         9 . A printed circuit board assembly comprising an electrical current sensing circuit, an analog-to-digital converter and a central processing unit connecting, wherein the electrical current sensing circuit comprises:
 a Wheatstone bridge circuit having at least four magnetoresistive elements connecting and a pair of output terminals, the magnetoresistive elements adapted for sensing an external magnetic field with a first direction generated by a carrying-current electrical conductor, and outputting a differential signal; and   a negative feedback circuit connecting with the output terminals, actuated by the differential signal and generated a magnetic field with a second direction that is opposite to the first direction, thereby eliminating the impact of the temperature drift to the magnetoresistive element character.   
     
     
         10 . The printed circuit board assembly according to  claim 9 , wherein the four magnetoresistive elements are divided into a first element pair and a second element pair that have two opposed pinning directions, which are perpendicular to the first direction of the external magnetic field. 
     
     
         11 . The printed circuit board assembly according to  claim 10 , wherein the negative feedback circuit comprises a preamplifier and a main wire, the preamplifier is connected with the output terminals, and the main wire is configured between the first element pair and second element pair and the configuring direction of the main wire is vertical with the pinning directions of the first element pair and the second element pair. 
     
     
         12 . The printed circuit board assembly according to  claim 10 , wherein the distance between the first element pair and the carrying-current electrical conductor is different from that between the second element pair and the carrying-current electrical conductor. 
     
     
         13 . The printed circuit board assembly according to  claim 10 , wherein the distance between the first element pair and the carrying-current electrical conductor is the same with that between the second element pair and the carrying-current electrical conductor. 
     
     
         14 . The printed circuit board assembly according to  claim 10 , wherein the first element pair has a first sensitivity and a first saturation point, and the second element pair has a second sensitivity and a second saturation point. 
     
     
         15 . The printed circuit board assembly according to  claim 14 , wherein the first sensitivity is equal to the second sensitivity, and the first saturation point is not equal to the second saturation point. 
     
     
         16 . The printed circuit board assembly according to  claim 14 , wherein the first sensitivity is not equal to the second sensitivity, and the first saturation point is not equal to the second saturation point. 
     
     
         17 . An electrical current sensor device comprising at least one printed circuit board assembly, a holder for holding the printed circuit board assembly, a shielding cover covering on the holder for shielding an external magnetic field generated by external environment, and a display device formed on the shielding cover and connected with the printed circuit board assembly; wherein the printed circuit board assembly comprises an electrical current sensing circuit comprising:
 a Wheatstone bridge circuit having at least four magnetoresistive elements connecting and a pair of output terminals, the magnetoresistive elements adapted for sensing an external magnetic field with a first direction generated by a carrying-current electrical conductor, and outputting a differential signal; and   a negative feedback circuit connecting with the output terminals, actuated by the differential signal and generated a magnetic field with a second direction that is opposite to the first direction, thereby eliminating the impact of the temperature drift to the magnetoresistive element character.